Modified conjugated diene polymer and method for preparing the same

ABSTRACT

Disclosed are a modified conjugated diene polymer and a method for preparing the same. The modified conjugated diene polymer and the method for preparing the same advantageously provide superior compatibility with an inorganic filler, heat generation, tensile strength and abrasion resistance, low fuel consumption and excellent resistance on wet roads.

This application is a National Stage Application of InternationalApplication No. PCT/KR2013/000892, filed Feb. 4, 2013, and claimspriority to and the benefit of Korean Patent Application No.10-2012-0011617, filed on Feb. 6, 2012, and Korean Patent ApplicationNo. 10-2013-0011063, filed on Jan. 31, 2013, the disclosures of whichare incorporated herein by reference in their entirety.

TECHNICAL FIELD

The present invention relates to a modified conjugated diene polymer anda method for preparing the same. The present invention relates to amodified conjugated diene polymer which exhibits superior compatibilitywith an inorganic filler, heat generation, tensile strength and abrasionresistance, low fuel consumption and excellent resistance on wet roadsand a method for preparing the same.

BACKGROUND ART

Demands for stability, durability and low fuel consumption of vehiclesare increasing. Accordingly, there is an increasing demand for rubbersexhibiting excellent resistance on wet roads and mechanical strength andlow rolling resistance as materials for vehicle tires, in particular,tire treads contacting the road.

Conventional tire treads have been produced using a conjugated dienerubber mixed with an inorganic filler in order to reinforce theproperties described above, but have problems of great hysteresis lossor low dispersibility.

DISCLOSURE Technical Problem

Therefore, the present invention has been made in view of the aboveproblems, and it is one object of the present invention to provide amodified conjugated diene polymer which exhibits superior compatibilitywith an inorganic filler, heat generation, tensile strength and abrasionresistance, low fuel consumption and excellent resistance on wet roads,and a method for preparing the same.

It is another object of the present invention to provide a rubbercomposition comprising the modified conjugated diene polymer and a tirecomprising the rubber composition.

It is yet another object of the present invention to provide a modifyingagent used for preparation of the modified conjugated diene polymer.

The objects and other objects can be accomplished by the presentinvention described below.

Technical Solution

In accordance with one aspect of the present invention, provided is amodified conjugated diene polymer represented by the following Formula1:

wherein R₁ is an alkyl group or an alkylsilyl group, R₂ is an alkylgroup or an alkylene group, R₃ and R₄ are an alkyl group, a is aninteger of 1 to 3, 1 and k are an integer of 0 to 2, m is an integer of1 to 3, l+k+m satisfy 3, p is a conjugated diene polymer chain, and b isan integer of 1 to 3, wherein two R₁ bonded to nitrogen, when k is 2,may be identical or different, and in the same way, when l and m are 2or more, the relevant groups may be identical or different.

In accordance with another aspect of the present invention, provided isa method for preparing a modified conjugated diene polymer comprising(a) polymerizing a conjugated diene monomer, or a conjugated dienemonomer and an aromatic vinyl monomer in the presence of a solvent usingan organometallic compound to prepare an active polymer having a metalend group, and (b) adding a compound represented by the followingFormula 2 to the active polymer to modify the active polymer:

wherein R₁ is an alkyl group or an alkylsilyl group, R₂ is an alkylgroup or an alkylene group, R₃ and R₄ are an alkyl group, a is aninteger of 1 to 3, and n is an integer of 0 to 2, wherein two R₁ bondedto nitrogen may be identical or different when n is 2, and in the sameway, when 3-n is 2 or more, the relevant groups may be identical ordifferent.

In accordance with another aspect of the present invention, provided isa modified conjugated diene polymer rubber composition comprising 0.1 to200 parts by weight of an inorganic filler with respect to 100 parts byweight of the modified conjugated diene polymer.

In accordance with another aspect of the present invention, provided isa tire comprising the modified conjugated diene polymer rubbercomposition.

In accordance with yet another aspect of the present invention, providedis a modifying agent used for preparation of the modified conjugateddiene polymer.

Advantageous Effects

As apparent from the fore-going, the present invention advantageouslyprovides a modified conjugated diene polymer which exhibits superiorcompatibility with an inorganic filler, heat generation, tensilestrength and abrasion resistance, low fuel consumption and excellentresistance on wet roads, and a method for preparing the same.

BEST MODE

Hereinafter, the modified conjugated diene polymer, the method forpreparing the same, the rubber composition comprising the modifiedconjugated diene polymer and the tire comprising the rubber compositionwill be described in detail.

The modified conjugated diene polymer according to the present inventioncomprises a polymer represented by the following Formula 1:

wherein R₁ is an alkyl group or an alkylsilyl group, R₂ is an alkylgroup or alkylene group, R₃ and R₄ are an alkyl group, a is an integerof 1 to 3, 1 and k are an integer of 0 to 2, m is an integer of 1 to 3,l+k+m satisfy 3, p is a conjugated diene polymer chain, and b is aninteger of 1 to 3, wherein two R₁ bonded to nitrogen, when k is 2, maybe identical or different, and similarly, corresponding groups, when land m are 2 or more, may be identical or different.

R₁ is for example a C1-C12 alkyl group or a C1-C12 alkylsilyl group.

R₂ is for example a C1-C12 alkyl group or a C1-C12 alkylene group.

R₃ and R₄ are for example a C1-C12 alkyl group.

l is for example 0 or 1.

k is for example 0 or 1. Within this range, there are advantages in thathysteresis loss is reduced, and compatibility with an inorganic filler,in particular, silica is excellent.

m is for example 1 or 2 and, in another example, m is 2 or 3.

The total number of p is 1 to 9, 1 to 5, or 1 to 3. Within this range,there is an advantage in that produced tires exhibit superior resistanceon wet roads and low fuel consumption.

In Formula 1, for example, k is 1, l is 0, and m is 2.

In Formula 1, in another example, k is 1, l is 1, and m is 1.

The conjugated diene polymer chain is for example a chain comprising aconjugated diene monomer alone, or the conjugated diene monomer and anaromatic vinyl monomer.

In another example, the conjugated diene polymer chain may be a polymerchain comprising 0.0001 to 40% by weight, 10 to 35% by weight or 20 to30% by weight of the aromatic vinyl monomer, based on 100% by weight intotal of the conjugated diene monomer and the aromatic vinyl monomer.

The polymer chain comprising the conjugated diene monomer and thearomatic vinyl monomer may be for example a random polymer chain.

The conjugated diene monomer is for example selected from the groupconsisting of 1,3-butadiene, 2,3-dimethyl-1,3-butadiene, piperylene,3-butyl-1,3-octadiene, isoprene, 2-phenyl-1,3-butadiene and mixturesthereof.

The aromatic vinyl monomer is for example selected from the groupconsisting of styrene, α-methylstyrene, 3-methylstyrene,4-methylstyrene, 4-propylstyrene, 1-vinylnaphthalene,4-cyclohexylstyrene, 4-(p-methylphenyl)styrene,1-vinyl-5-hexylnaphthalene and mixtures thereof. In another example, thearomatic vinyl monomer is styrene or α-methylstyrene.

The modified conjugated diene polymer, for example, has a Mooneyviscosity of 40 or higher, or 40 to 90.

In another example, the modified conjugated diene polymer may have aMooney viscosity of 45 to 85, or 50 to 80.

The modified conjugated diene polymer, for example has a number averagemolecular weight of 1,000 to 2,000,000 g/mol, 10,000 to 1,000,000 g/mol,or 100,000 to 500,000 g/mol.

The conjugated diene polymer, for example, has a vinyl content of 18% orhigher, 25% or higher, 30 to 70%, or 40 to 60%. Within this range, thereare advantages in that glass transition temperature of polymer isincreased, properties such as running resistance and brake power,required for produced tires are satisfied and fuel consumption isreduced.

The vinyl content means a content of a unit having a vinyl group, or acontent of a 1,2-added conjugated diene monomer rather than a 1,4-addedconjugated diene monomer with respect to 100% by weight of theconjugated diene monomer.

The modified conjugated diene polymer may for example have a PDI of 0.5to 10, 0.5 to 5, or 1.0 to 2.0.

Regarding viscoelasticity, the modified conjugated diene polymer forexample has a Tan 6 at 0° C., measured at 10 Hz using DMA after mixingwith silica, of 0.6 to 1 or 0.9 to 1. Within this range, resistance onroad or wet road is greatly improved, as compared to the prior art.

In addition, the modified conjugated diene polymer has, for example, aTan 6 at 60° C., of 0.06 to 0.09, or 0.07 to 0.08. Within this range,rolling resistance or rotational resistance (RR) is advantageouslygreatly improved.

The method for preparing a modified conjugated diene polymer accordingto the present invention includes (a) polymerizing a conjugated dienemonomer, or a conjugated diene monomer and an aromatic vinyl monomer inthe presence of a solvent using an organometallic compound to prepare anactive polymer having a metal end group, and (b) adding a compoundrepresented by the following Formula 2 to the active polymer to modifythe active polymer:

wherein R₁ is an alkyl group or an alkylsilyl group, R₂ is an alkylgroup or an alkylene group, R₃ and R₄ are an alkyl group, a is aninteger of 1 to 3, and n is an integer of 0 to 2, wherein two R₁ bondedto nitrogen may be identical or different when n is 2, and similarly,corresponding groups may be identical or different when 3-n is 2 ormore.

n is for example 0 or 1.

R₁ to R₄ have been defined in above.

The conjugated diene monomer is for example selected from the groupconsisting of 1,3-butadiene, 2,3-dimethyl-1,3-butadiene, piperylene,3-butyl-1,3-octadiene, isoprene, 2-phenyl-1,3-butadiene and mixturesthereof.

The aromatic vinyl monomer is for example selected from the groupconsisting of styrene, α-methylstyrene, 3-methylstyrene,4-methylstyrene, 4-propylstyrene, 1-vinylnaphthalene,4-cyclohexylstyrene, 4-(p-methylphenyl)styrene,1-vinyl-5-hexylnaphthalene and mixtures thereof. In another example, thearomatic vinyl monomer is styrene or α-methylstyrene.

The aromatic vinyl monomer may be present in an amount of 0.0001 to 40%by weight, 10 to 35% by weight or 20 to 30% by weight, based on 100% byweight in total of the conjugated diene monomer and the aromatic vinylmonomer.

The solvent may for example comprise at least one selected from thegroup consisting of hydrocarbons, n-pentane, n-hexane, n-heptane,isooctane, cyclohexane, toluene, benzene and xylene.

The organometallic compound may for example comprise at least oneselected from the group consisting of organic alkali metal compounds,organolithium compounds, organosodium compounds, organopotassiumcompounds, organorubidium compounds and organocesium compounds.

In another example, the organometallic compound may comprise at leastone selected from the group consisting of methyl lithium, ethyl lithium,isopropyl lithium, n-butyl lithium, sec-butyl lithium, tert-butyllithium, n-decyl lithium, tert-octyl lithium, phenyl lithium, 1-naphthyllithium, n-eicosyl lithium, 4-butylphenyl lithium, 4-tolyl lithium,cyclohexyl lithium, 3,5-di-n-heptylcyclohexyl lithium and 4-cyclopentyllithium.

In another example, the organometallic compound is n-butyl lithium,sec-butyl lithium or a mixture thereof.

In another example, the organometallic compound may comprise at leastone selected from the group consisting of sodium naphthyl, potassiumnaphthyl, lithium alkoxide, sodium alkoxide, potassium alkoxide, lithiumsulfonate, sodium sulfonate, potassium sulfonate, lithium amide, sodiumamide and potassium amide. The organometallic compound may be used incombination with another organometallic compound.

The organometallic compound is for example used in an amount of 0.01 to10 mmol, 0.05 to 5 mmol, 0.1 to 2 mmol or 0.1 to 1 mmol, based on 100 gin total of the monomer.

A molar ratio of the organometallic compound to the compound representedby Formula 2 is for example 1:0.1 to 1:10, or 1:0.5 to 1:2.

The active polymer having a metal end group means a polymer wherein apolymer anion is bonded to a metal cation.

The method for preparing a modified conjugated diene polymer accordingto the present invention, for example, comprises further adding a polaradditive during (a) the polymerization.

The polar additive is for example a base. In another example, the polaradditive is ether, amine or a mixture thereof, or is selected from thegroup consisting of tetrahydrofuran, ditetrahydrofurfurylpropane,diethylether, cycloamylether, dipropyl ether, ethylmethylether,diethylene glycol, dimethyl ether, tertiary butoxyethoxyethanebis(2-dimethylaminoethyl)ether, (dimethylaminoethyl)ethylether,trimethylamine, triethylamine, tripropylamine, andtetramethylethylenediamine. In another example, the polar additive isditetrahydrofurfurylpropane, triethylamine ortetramethylethylenediamine.

The polar additive may be for example used in an amount of 0.001 to 50g, 0.001 to 10 g, 0.005 to 1 g, or 0.005 to 0.1 g, based on 100 g intotal of the added monomer.

In another example, the polar additive may be used in an amount of 0.001to 10 g, 0.005 to 1 g, or 0.005 to 0.1 g, based on 1 mmol in total ofthe added organometallic compound.

When the conjugated diene monomer and the aromatic vinyl monomer arecopolymerized, a block copolymer may be generally prepared due todifference in reaction speed between the monomers. However, when thepolar additive is added, reaction speed of the vinyl aromatic compoundwhich has a low reaction speed is increased, microstructure of thecopolymer corresponding thereto, for example, random copolymer isadvantageously induced.

The polymerization (a) may be for example anionic polymerization.

In another example, the polymerization (a) may be living anionicpolymerization for obtaining active ends by growth reaction by anions.

The polymerization (a) may be for example polymerization at an elevatedtemperature or polymerization at a fixed temperature.

The polymerization at an elevated temperature means a polymerizationmethod which includes elevating a reaction temperature by heating afteradding an organometallic compound. The polymerization at a fixedtemperature means a polymerization method which does not include heatingafter adding an organometallic compound.

A temperature of the polymerization (a) is for example −20 to 200° C., 0to 150° C. or 10 to 120° C.

In the modification (b), for example, one or more types, or two or threetypes of the compound represented by Formula 1 may be added.

In addition, the modification (b) may include reaction, for example, at0 to 90° C. for one minute to 5 hours.

The method for preparing a modified conjugated diene polymer accordingto the present invention may be, for example, batch or continuouspolymerization including one, two or more reactors.

The modified conjugated diene polymer may be, for example, preparedaccording to the method for preparing a modified conjugated dienepolymer.

The modified conjugated diene polymer rubber composition according tothe present invention comprises 0.1 to 200 parts by weight of aninorganic filler with respect to 100 parts by weight of the modifiedconjugated diene polymer.

The modified conjugated diene polymer rubber composition may furtherinclude, for example, another conjugated diene polymer.

The another conjugated diene polymer may be, for example,styrene-butadiene rubber (SBR), butadiene rubber (BR), natural rubber ora mixture thereof.

The SBR may be, for example, a solution styrene-butadiene rubber (SSBR).

The modified conjugated diene polymer rubber composition according tothe present invention may, for example, include 20 to 100 parts byweight of the modified conjugated diene polymer and 0 to 80 parts byweight of the another conjugated diene polymer.

In another example, the modified conjugated diene polymer rubbercomposition may include 20 to 99 parts by weight of the modifiedconjugated diene polymer and 1 to parts by weight of the anotherconjugated diene polymer.

In another example, the modified conjugated diene polymer rubbercomposition may include 10 to 100 parts by weight of the modifiedconjugated diene polymer, 0 to 90 parts by weight of the anotherconjugated diene polymer, 0 to 100 parts by weight of carbon black, 5 to200 parts by weight of silica and 2 to 20 parts by weight of a silanecoupling agent.

In another example, the modified conjugated diene polymer rubbercomposition may include 10 to 100 parts by weight of the modifiedconjugated diene polymer, 0 to 90 parts by weight of the anotherconjugated diene polymer, 0 to 100 parts by weight of carbon black, 5 to200 parts by weight of silica and 2 to 20 parts by weight of a silanecoupling agent, wherein a total weight of the modified conjugated dienepolymer and the another conjugated diene polymer is 100 parts by weight.

In another example, the modified conjugated diene polymer rubbercomposition according to the present invention is prepared by mixing 100parts by weight of a polymer mixture including 10 to 99% by weight ofthe modified conjugated diene polymer and 1 to 90% by weight of theanother conjugated diene polymer with 1 to 100 parts by weight of carbonblack, 5 to 200 parts by weight of silica and 2 to 20 parts by weight ofa silane coupling agent.

The inorganic filler may be present in an amount of, for example, 10 to150 parts by weight, or 50 to 100 parts by weight.

The inorganic filler may be, for example, carbon black, a silica filleror a mixture thereof.

In another example, the inorganic filler may be silica. In this case,advantageously, dispersibility is greatly improved and hysteresis lossis greatly decreased because silica particles are bonded to (capped to)an end of the modified conjugated diene polymer.

The modified conjugated diene polymer rubber composition may for examplefurther include 1 to 100 parts by weight of an oil.

The oil may be, for example, a mineral oil, a softening agent or thelike.

The oil may be for example used in an amount of 10 to 100 parts byweight or 20 to 80 parts by weight, with respect to 100 parts by weightof the conjugated diene copolymer. Within this range, there areadvantages in that properties are efficiently exhibited, the rubbercomposition is suitably softened and processability is thus excellent.

The modified conjugated diene polymer rubber composition may be forexample used as a material for tires or tire treads.

The tire may be produced from a material containing the modifiedconjugated diene polymer rubber composition.

The modifying agent according to the present invention is represented bythe following Formula 2:

wherein R₁ is an alkyl group or an alkylsilyl group, R₂ is an alkylgroup or an alkylene group, R₃ and R₄ are an alkyl group, a is aninteger of 1 to 3, and n is an integer of 0 to 2, wherein two R₁ bondedto nitrogen may be identical or different when n is 2, and similarly,corresponding groups may be identical or different when 3-n is 2 ormore.

Hereinafter, preferred examples will be provided for betterunderstanding of the present invention. These examples are only providedto illustrate the present invention and it will be apparent to thoseskilled in the art that various modifications and alterations arepossible within the scope and technical range of the present invention.Such modifications and alterations fall within the scope of claimsincluded herein.

EXAMPLE Example 1

260 g of styrene, 720 g of 1,3-butadiene, 5,000 g of normal hexane, and1.3 g of 2,2-bis(2-oxolanyl)propane as a polar additive were added to a20 L autoclave reactor and an inner temperature of the reactor waselevated to 40° C. When the inner temperature of the reactor reached 40°C., 4 mmol of n-butyl lithium was added to the reactor and an adiabatictemperature-rising reaction was proceeded until the reaction wasstabilized. 20 minutes after the adiabatic temperature-rising reactionwas finished, 20 g of 1,3-butadiene was added to the reactor. After 5minutes, 5 mmol of bis(methyldimethoxysilylpropyl)-N-methylamine wasadded to the reactor and reaction was proceeded for 15 minutes. Then,polymerization reaction was stopped using ethanol and 5 ml of a 0.3 wt %solution of butylated hydroxytoluene (BHT) as an antioxidant in hexanewas then added to the reaction mixture.

The polymerization product was added to warm water heated by steam, themixture was stirred, the solvent was removed, and the resulting solutionwas then roll-dried to remove the residual solvent and water, therebyproducing a modified conjugated diene polymer. Analysis results of themodified conjugated diene polymer thus produced are shown in thefollowing Table 1.

Example 2

A modified conjugated diene polymer was prepared in the same manner asin Example 1, except that 0.8 g of 2,2-bis(2-oxolanyl)propane was addedas a polar additive. Analysis results of the modified conjugated dienepolymer are shown in the following Table 1.

Example 3

A modified conjugated diene polymer was prepared in the same manner asin Example 2, except that bis(trimethoxysilylpropyl)-N-methylamine wasused as a modifying agent, instead ofbis(methyldimethoxysilylpropyl)-N-methylamine. Analysis results of themodified conjugated diene polymer are shown in the following Table 1.

Example 4

A modified conjugated diene polymer was prepared in the same manner asin Example 1, except that diethylaminopropyl trimethoxysilane was used,instead of bis(methyldimethoxysilylpropyl)-N-methylamine. Analysisresults of the modified conjugated diene polymer are shown in thefollowing Table 1.

Comparative Example 1

Analysis results of an unmodified conjugated diene polymer (5025-2HM,produced by Lanxess Deutschland Gmbh) which is the most commonly soldare shown in the following Table 1.

Comparative Example 2

A modified conjugated diene polymer was prepared in the same manner asin Example 2, except that 1.2 mmol of dimethyldichlorosilane as acoupling agent was added, instead ofbis(methyldimethoxysilylpropyl)-N-methylamine as a modifying agent.Analysis results of the modified conjugated diene polymer are shown inTable 1.

Analysis of conjugated diene polymers prepared in Examples 1 to 4 andComparative Examples 1 to 2 was performed in accordance with thefollowing method.

a) Mooney viscosity: two specimens having a weight of 15 g or more werepre-heated for one minute using MV-2000 produced by ALPHA Technologiesand Mooney viscosity thereof was measured at 100° C. for 4 minutes.

b) Styrene monomer (SM) and vinyl content: measured using NMR.

c) Weight average molecular weight (Mw), number average molecular weight(Mn) and molecular weight distribution (PDI): measured by GPC at 40° C.At this time, a combination of two pieces of PLgel Olexis columnsproduced by Polymer Laboratories and one piece of PLgel mixed-C columnwas used as a column. All newly replaced columns were mixed bed-typecolumns. In addition, polystyrene (PS) was used as a GPC standardmaterial for determination of molecular weight.

TABLE 1 Comparative Examples Examples Type 1 2 3 4 1 2 Sample A B C D EF n-butyllithium 4 4 4 4 — 4 (mmol) Polar additive 1.3 0.8 0.8 1.3 0.8(g) Modifying a 12 12 — — — — agent b — — — 12 — — (mmol) c — — 12 — — —Coupling d — — — — 1.2 agent TDAE oil phr — — — — 37.5 — Mooneyviscosity 54 74 70 50 61 66 (MV) NMR (%) SM 26 26 26 26 26 26 Vinyl 5044 45 47 50 44 GPC(×10⁴) Mn 30 32 25 30 39 31 Mw 49 39 33 50 69 37 PDI1.6 1.2 1.3 1.7 1.8 1.2 a: bis(methyldimethoxysilylpropyl)-N-methylamineb: diethylaminopropyltrimethoxysilane c:bis(trimethoxysilylpropyl)-N-methylamine d: dimethyldichlorosilane

TABLE 2 (Unit: parts by weight) S-1 S-2 Rubber 100.0 137.5 Silica 70.070.0 Coupling 11.02 11.2 agent Oil 33.75 — Zinc 3.0 3.0 Stearic acid 2.02.0 Antioxidant 2.0 2.0 Anti-aging 2.0 2.0 agent Wax 1.0 — Rubber 1.751.75 accelerator Sulfur 1.5 1.5 Vulcanization 2.0 2.0 accelerator Totalweight 230.2 234.0

A, B, C, D, E and F among samples shown in Table 1 were used as rubberraw materials and were mixed under mixing conditions shown in thefollowing Table 3 to prepare conjugated diene polymer rubbercompositions. A, B, C, D and F were mixed under mixing conditions of S-1and E was mixed under mixing conditions of S-2.

The mixing of the rubber compositions of the conjugated diene polymerwas performed using a Banbury mixer equipped with a temperaturecontroller as follows. In primary mixing, a rubber raw material(conjugated diene polymer), a filler, an organosilane coupling agent, anoil, zinc, a stearic acid antioxidant, an anti-aging agent, a wax andaccelerators were primarily mixed at 80 rpm. At this time, thetemperature of the mixer was controlled and a primary mixture wasobtained at a discharge temperature of 140 to 150° C. In secondarymixing, after the primary mixture was cooled to room temperature, arubber, sulfur and a vulcanization accelerator were added to a mixer anda secondary mixture was obtained at a discharge temperature of 45 to 60°C. In tertiary mixing, the secondary mixture was molded and wasvulcanized using a vulcanization press at 180° C. for T90+10 minutes toprepare a vulcanized rubber.

Physical properties of the prepared vulcanized rubbers were measured inaccordance with the following method.

1) Tensile Strength Test

Tensile strength at break and tensile strength at an elongation of 300%(300% modulus) of specimens were measured by tensile strength testing inaccordance with ASTM 412.

2) Viscoelasticity

A dynamic mechanical analyzer produced by TA Instrument was used. Tan 6was measured while varying strain in a torsional mode at a frequency of10 Hz at different measurement temperatures of 0 to 60° C. Payne effectwas indicated as a difference between a minimum and a maximum at astrain of 0.2% to 40%. As payne effect decreases, dispersibility offiller such as silica is improved. As Tan 6 at a low temperature of 0°C. increases, resistance on wet roads is improved, and as Tan 6 at ahigh temperature of 60° C. decreases, hysteresis loss is low, androlling resistance, that is, fuel consumption, of tires, is reduced.Physical properties of vulcanized rubbers are shown in Table 3.

TABLE 3 Compar- Compar- Exam- Exam- Exam- Exam- ative ative Item ple 5ple 6 ple 7 ple 8 Example 3 Example 4 Sample A B C D E F 300% 123 123130 108 98 104 modulus (Kgf/cm²) Tensile 184 188 167 162 161 168strength (Kgf/cm²) Tan δ at 0.986 0.851 0.881 0.881 0.547 0.542 0° C.Tan δ at 0.075 0.066 0.080 0.085 0.085 0.098 60° C. ΔG′ at 0.34 0.350.35 0.38 0.56 0.74 60° C. (payne effect)

As can be seen from Table 3 above, the modified conjugated diene polymerrubber compositions according to Examples 5 to 8 exhibited a greatincrease in 300% modulus (tensile strength) and tensile strength, and ahigh Tan 6 at 0° C., as compared to Comparative Examples 3 and 4, whichindicates that tires comprising the modified conjugated diene polymeraccording to the present invention exhibited superior resistance on wetroads.

In addition, the modified conjugated diene polymers of Examples 5 to 8exhibited a low Tan 6 at 60° C., as compared to Comparative Examples 3and 4. Tires comprising the modified conjugated diene polymer accordingto the present invention exhibited low rolling resistance as compared tothe prior art.

In addition, the modified conjugated diene rubber copolymers of Examples5 to 8 according to the present invention exhibited considerably low ΔG′at 60° C., as compared to Comparative Examples 3 and 4, which indicatesthat dispersibility of silica is greatly improved.

What is claimed is:
 1. A modified conjugated diene polymer representedby the following Formula 1:

wherein R1 is an alkyl group, R2 is an alkylene group, R3 and R4 are analkyl group, a is an integer of 1 to 3, l and k are 1, m is 1, p is aconjugated diene polymer chain, and b is an integer of 1 to 3, wherein bis not greater than a.
 2. The modified conjugated diene polymeraccording to claim 1, wherein the conjugated diene polymer chain is arandom copolymer chain comprising a conjugated diene monomer and anaromatic vinyl monomer.
 3. The modified conjugated diene polymeraccording to claim 1, wherein the modified conjugated diene polymer hasa number average molecular weight of 1,000 to 2,000,000 g/mol.
 4. Themodified conjugated diene polymer according to claim 1, wherein themodified conjugated diene polymer has a vinyl content of 18% or more. 5.The modified conjugated diene polymer according to claim 1, wherein themodified conjugated diene polymer comprises 10 to 40% by weight of thearomatic vinyl monomer, based on 100% by weight in total of theconjugated diene monomer and the aromatic vinyl monomer.
 6. The modifiedconjugated diene polymer according to claim 1, wherein the modifiedconjugated diene polymer has a Mooney viscosity of 40 or more.